1. Field
The present disclosure relates generally to inspecting objects and, in particular, to performing non-destructive inspection of objects.
2. Background
When objects are manufactured or assembled, it is often desirable to determine whether those objects meet different requirements. For example, when parts are welded to each other, a determination may be made as to whether inconsistencies are present in the weld. As another example, in manufacturing objects such as skin panels, spars, and other structures from composite materials, it is often desirable to determine whether inconsistencies are present in the objects. Inconsistencies may take the form of voids, delaminations, and other types of inconsistencies.
In testing these objects, it is often desirable to perform tests without permanently changing the objects. For example, cutting or performing other tests that may change the objects on a permanent basis is undesirable because these changes may render the objects unusable.
Non-destructive inspection is a type of testing that does not permanently alter an object in an undesired manner. In other words, the object may still be used for its intended purpose after non-destructive inspection of the object. Non-destructive inspection may include ultrasonic testing, x-ray testing, visual inspection, eddy current testing, and other suitable types of testing.
With ultrasonic testing, transducers are used to generate and detect acoustic waves in an object. These transducers often take the form of piezoelectric transducers.
With this type of transducer, the transducer is placed in contact with the object being tested. The transducer is typically coupled to the test object by a coupling medium. This coupling medium may be, for example, water, oil, or some other suitable medium.
The transducer generates acoustic waves in the test object. A response to the acoustic waves is received by the transducer. This response is analyzed to perform the inspection. In particular, the response may be analyzed to determine whether any inconsistencies are present in the test object.
In some cases, contact between the transducer and the test object may be undesirable. Further, the use of a coupling medium also may be undesirable.
In these cases, an electromagnetic acoustic transducer (EMAT) may be used in place of traditional piezoelectric transducers. Electromagnetic acoustic transducers may be particularly useful for automated inspections and inspections in hot and cold environments.
An electromagnetic acoustic transducer may be used both to generate acoustic waves and detect responses to the acoustic waves. An electromagnetic acoustic transducer uses an electromagnetic mechanism to generate the acoustic waves. With this type of transducer, a coupling medium may be unnecessary.
Electromagnetic acoustic transducers, however, may not be ideal for all types of materials and test objects. For example, materials that have low conductivity may not be ideal candidates for testing with electromagnetic acoustic transducers. Electromagnetic acoustic transducers may not operate at as large a stand-off distance as desired or may not detect inconsistencies as small as desired.
Therefore, it would be advantageous to have a method and apparatus that takes into account at least some of the issues discussed above, as well as possibly other issues.